Smart cards are plastic cards that incorporate an integrated circuit (IC) chip with some form of memory. Many smart cards are wallet-sized, as specified by International standard organization (ISO) standards. These international standards specify physical characteristics of cards, transmission protocols, and rules for applications and data elements.
Memory-based smart cards include memory and some non-programmable logic. Such cards may be used as personal identification cards or phone cards. More complex processor-based smart cards may include a central processing unit (CPU) and ROM for storing an operating system, a main memory (RAM), and a memory section for storing application data (usually an EEPROM). Processor-based smart cards may be used where heavy calculations or more security is required.
Smart cards may fall into one of two categories: contact and contactless. Contact cards must be inserted into a card reader to be accessed. Contact cards include an interconnect module, usually gold plated, with contact pads. The interconnect module may include power, reset, ground, serial input/output (SIO), and clock signal contact pads, as laid out in ISO 7816. The contact pads are physically contacted by pins in the reader to power and communicate with the IC chip. Contact cards are commonly used as telephone prepayment cards and bank cards.
Contactless cards do not require contact with the reader to be accessed. Contactless cards include an antenna embedded in the card which may be used for power transmission and communication by radio signals or capacitive inductance. Some advantages of contactless cards over contact cards include faster transactions, ease of use, and less wear and tear on the cards and readers.
The antennas may be embedded in the card by ultrasonically heating a wire and implanting the heated wire into the plastic of the card substrate in a desired antenna pattern. The parameters which determine the success and quality of an implanted antenna are the amount of ultrasonic energy used to heat the wire, and the pressure and speed of implantation. With regard to pressure, if the implanting head applies too much pressure, the writing horn may run into the plastic and plastic may power back up into the tool. However, if too little pressure is applied, the wire may not embed into the plastic at all. Accordingly, it is desirable to precisely control the pressure applied during implantation.
In an embodiment, a system for implanting a wire antenna in a contactless smart card includes an ultrasonic implanting head with a voice-coil actuator to control the pressure at which a heated wire is forced into a plastic card substrate. The force produced by the actuator is proportional to the current in a coil winding in the actuator.
A controller uses a feedback system to maintain a relatively constant applied pressure. The feedback system monitors the current in the coil and the controller issues electronic signals to increase or decrease the current in the coil in response to the monitored current.